JERUSALEM, June 13 — Gunmen from the Hamas party further consolidated their control of northern Gaza today, seizing additional security buildings and a key north-south road, and killing fighters from the rival Fatah party.

Fatah held on to parts of Gaza, but was increasingly outgunned and hemmed in by Hamas, which ordered the Fatah fighters in the north to lay down their arms by 7 p.m. Friday, local time. There was no immediate response from Fatah.

Hamas, which follows an Islamist ideology, killed at least nine Fatah fighters in gun battles and 13 more in a grenade and mortar attack on a security building in the town of Khan Yunis, Reuters reported.

“What is happening in Gaza is madness,” the Palestinian president, Mahmoud Abbas, who is the leader of Fatah. told reporters on the West Bank today.

Fatah said it was suspending its participation in the joint “unity” government until the fighting with Hamas ends.

The United Nations said that it would scale back its operations in Gaza after two Palestinians who worked for a U.N. agency were killed in the fighting there, The Associated Press reported. The United Nations Relief and Works Agency"